Drug addiction persists as a significant global social concern with a negative impact on social harmony and stability that cannot be ignored. After returning to society, individuals with drug addiction often suffer from impaired creative problem-solving abilities and difficulties in interpersonal cooperation. The difficulties in survival stress and the sense of helplessness triggered by these factors are important reasons that lead them to seek drugs repeatedly and even to commit criminal behaviors. Therefore, enhancing creative realistic problem-solving abilities emerges as a pivotal pathway for drug addicts to facilitate rehabilitation from drug addiction and achieve societal adaptation. The project emphasizes both individual and collaborative creative solution generation for realistic problem solving. The abnormal cognitive neural mechanisms and interpersonal neural mechanisms will be systematically explored by using multiple cognitive and neuroimaging methods, such as functional near-infrared spectroscopy (fNIRS), electroencephalography (EEG), and eye-tracking. From the cognitive-behavioral-brain level, a comprehensive neurophysiological multimodal predictive model of how drug addiction affects creative realistic problem-solving will be constructed by multi-level data fitting modeling. Building upon this research foundation, The investigators will further implement single and repeated sessions of transcranial direct current stimulation (tDCS) targeting damaged brain regions for the intervention of individual and collaborative problem-solving ability under the effect of drug addiction. The indicators of brain, cognition, and behavior will be tracked at multiple time points.

Inclusion Criteria:

• age between 30 and 60 years;
• fulfilling the diagnostic criteria for severe substance use disorder as specified in the Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders.
• a history of heroin use exceeding ten years, with a daily average intake of at least 0.1 grams.
• abstinence duration of eight months or less, with a positive result of a urine test before entering the rehabilitation center.
• no history of neuromodulation treatments such as tDCS within the past six months.

Exclusion Criteria:

• a history of alcohol dependence, neurological disorders, or other complex psychiatric conditions.
• the presence of intracranial metallic implants or elevated intracranial pressure.
• a history of epilepsy or recent electroencephalogram evidence of epileptiform activity.
• the use of implanted electronic devices, such as pacemakers;.
• scalp hyperalgesia or a tendency toward bleeding.
• severe cardiac conditions.

This study is a government-collaborative project involving sensitive personal information of a vulnerable population, and as such, it is imperative to adhere to strict confidentiality protocols. All data collected will be handled in compliance with ethical guidelines and legal requirements to ensure the protection of participants' privacy.